1. Field of the Invention
The present invention relates to an apparatus and method for detecting and quantifying magnetic field gradients and their effects by measuring magnetically induced forces acting on a spin-containing particle mounted on a mechanical oscillator. A spin-containing particle may include any material that displays a magnetic moment in the presence of a magnetic field. The spin-containing particle has a modulated magnetic moment with a temporal response that matches the resonance frequency of the mechanical oscillator due to the action of a spatially uniform polarizing field that has a temporal response that matches the resonance frequency of the mechanical oscillator.
2. Related Art
Related Art relevant to the present invention includes:                [1] U.S. Pat. No. 5,266,896, 1993, D. Rugar, J. Sidles, and C. Yannoni, “Mechanical detection and imaging of magnetic resonance by magnetic moment modulation,”        [2] U.S. Pat. No. 5,017,010, 1991, H. J. Mamin and D. Rugar, “High sensitivity position sensor and method,”        [3] S. J. Swithenby, “SQUIDS and their applications in the measurement of weak magnetic fields,” J. Phys. E: Sci. Instrum., vol. 13, pp. 801-813, 1980.        [4] D. F. L. Jenkins, M. J. Cunningham, W. W. Clegg, and M. M. Bakush, “Measurement of the modal shapes of inhomogeneous cantilevers using optical beam deflection,” Meas. Sci. Technol., vol. 6, pp. 160-166, 1995.        [5] S. Rast, C. Wattinger, U. Gysin, and E. Meyer, “The noise of cantilevers,” Nanotechnology, vol. 11, pp. 169-172, 2000.        [6] T. R. Albrecht, P. Grütter, D. Rugar, and D. P. E. Smith, “Low-temperature force microscope with all-fiber interferometer,” ultramicroscopy, vol. 42-44, pp. 1638-1646, 1992.        [7] T. D. Stowe, K. Yasumura, T. W. Kenny, D. Botkin, K. Wago, and D. Rugar, “Attonewton force detection using ultrathin silicon cantilevers,” App. Phys. Lett., vol. 71, pp. 288-290, 1977.        [8] J. A. Marohn, R. Fainchtein, and D. D. Smith, “An optimal magnetic tip configuration for magnetic resonance force microscopy of microscale buried features,” Applied Physics Letters, vol. 73, pp. 3778-3780, 1998.        